quality of fly ash bricks
quality of fly ash bricks

1. normal quality

  • Bricks should be free from cracks and defects and free from lumps of lime.
  • Bricks will have smooth rectangular faces with sharp corners
  • bricks are of the same color
  • The ratio of soil and fly ash shall be as per IS-2117-1991.
  • Fly ash used in the manufacture of bricks shall conform to Grade 1 or Grade 2 as per IS-3812-1981.
  • The frog shape of a hand cast brick with a height of 90 mm or 70 mm will be as shown in the figure below.
Frog Shape For Burnt Clay Fly Ash Building Bricks
Frog Shape For Burnt Clay Fly Ash Building Bricks

2. Dimensional Requirements

Dimensions for Modular Bricks
Length (L), mm Width (W), mm Height (H), mm
190 90 90
190 90 40
Dimensions for non-modular bricks
Length (L), mm Width (W), mm Height (H), mm
230 110 70
230 110 30

3. physical requirements

pressure force The minimum average compressive strength shall be according to the different class of the group (see table below). The compressive strength of any individual brick should not be less than the minimum compressive strength for the respective class of brick. (see Table below)
water absorption Not more than 20% by weight up to class 12.5 and 15% by weight for higher classes.
flourish The class should not exceed ‘Medium’ till 12.5 and ‘Moderate’ for the upper class.

4. Burnt Clay Fly Ash Bricks Classes

class designation average compressive strength
n/mm2 kg/cm2,About)
30 30 300
25 25 250
20 20 200
17.5 17.5 175
15 15 150
12.5 12.5 125
10 10 100
7.5 7.5 75
5 5 50
3.5 3.5 35


IS-13757-1993 – Specification for fly ash construction bricks

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.